Users performing frequent repetitions of motions which put stress on the hand or arm may suffer from carpal tunnel syndrome. This is caused by injury to tendons of the wrist which become inflamed by excessive repetition of he same movements.
Tendons and nerves in the wrists pass through the a carpal tunnel between the wrist and the fingers. The tunnel formed by bones and ligaments in the wrist narrows toward the palm of the hand, and nerves that reach toward the fingers may become pinched, causing pain. Hand tools used for repetitive task may cause such strain on the hand that carpal tunnel syndrome occurs in the tool user. In a non-limiting example, squeegees used for spreading fluid in silkscreen printing are frequently designed so that they must be gripped in such a stressful manner that strain is placed on the wrist tendons, and workers using such tools are liable to acquire carpal tunnel injuries.
Known spreaders, such as described in Barnby, U.S. Pat. No. 3,110,919, have an angular upper edge which is not contoured to the shape of the hand. Akers, U.S. Pat. No. 3,676,888, describes an adjustable squeegee for applying synthetic sealing material to damaged surfaces of automobile bodies or the like which may be made in one piece having a stiffening rod through the upper portion, or the upper portion may be formed separately and the blade attached. The upper edge does not conform to the shape of the hand.
Pfeifer, U.S. Pat. No. 4,254,527, describes a window cleaning implement having a short handle attached directly to one side of the plate. The handle of Pfeifer is designed so that it only requires holding with the fingers and not with the entire palm of the hand. The patent to Loos, U.S. Pat. No. 4,297,761, describes a multi-purpose garbage disposal utensil for scraping material into a garbage disposer. The top surface is horizontally flattened, not shaped to fit the palm of a hand.
Other known handles for tools such as squeegees have a symmetrical teardrop shaped cross-section which cannot accommodate a user's fingertips and opposing thumb.